In recent years, in a field of display devices to display images, there has been developed and commercialized a display device (an organic EL display device) using current-driven optical elements, e.g., organic EL (Electro Luminescence) elements, that are configured to be varied in emission intensity according to values of currents flowing therethrough. Unlike liquid crystal elements or the like, organic EL elements are spontaneous light emitting elements, involving no light source (backlight). Therefore, an organic EL display device has features such as higher visible recognizability, lower power consumption, and higher response speed of elements, as compared to those of a liquid crystal display device that involves a light source. Such an organic EL device is often adopted in medium-sized or small-sized display devices.
For example, Patent Literature 1 discloses a so-called active matrix display device in which each pixel is provided with a thin film transistor (TFT) to control light emission of organic EL elements for each pixel. This display device may include a plurality of horizontally extending gate lines and a plurality of vertically extending data lines with pixels provided in the vicinity of respective intersections of the gate lines and the data lines. Thus, pixels are selected line by line based on signals of the gate lines to allow analog pixel voltages to be written in the pixels thus selected.